The hypotheses tested in these studies were 1) Endothelial cell growth factor (ECGF) may play a role in the transformation of skeletal muscle by chronic stimulation from an easily fatigable state to one of fatigue-resistance. 2) Transformed skeletal muscle responds to catecholamine in a manner different to that of non- transformed skeletal muscle. Conditioned latissimus dorsi muscles of dogs were created using an implanted pacemaker. Serial biopsies of the stimulated and contralateral none stimulated muscles were performed for ECGF and histology. At sacrifice dose-response experiments to catecholamine will be conducted to determine if slow fiber transformation alters pharmacologic responses.